1. Field of the Invention
This invention relates to a method and apparatus for cutting elongated material into shorter lengths having predetermined dimensions. More particularly, this invention relates to a method of cutting a plurality of different elongated materials, preferably continuous filament, into shorter lengths at the same time in a single cutter assembly to provide a good mix of the materials. The preferred elongated material of the present invention is continuous filamentary material, preferably of polyester, nylon, Kevlar.RTM., fiberglass, etc.; elongated material may equally be applicable to strips, ribbons, tapes, film, wire or any other flexible material. The material is preferably used as reinforcement for plastic products.
2. The Prior Art
In the current practice of handheld spray molding of plastic products such as bathtubs, showers, boats, etc., glass fibers are fed from a creel package to an air driven cutter mechanism attached to the plastic spray gun. The gun sprays a resin and catalyst into a mold; a cutter simultaneously chops the fiberglass into staple lengths which are mixed with the stream of resin as it exits the spray nozzle of the gun. The cutter mechanism includes cutting blades rotated against a polyurethane covered roll and between which the fiberglass is passed to be cut or broken into lengths corresponding to the spacing of the cutting blades. The design has not proved satisfactory in cutting less brittle materials such as polyester yarn. The present invention is intended to allow elongated materials to be cut into staple lengths and delivered to the spray stream of a handheld spray gun, and in fact, permits the simultaneous cutting of several different elongated materials for formation of hybrid filamentary of reinforcement of plastics.
The abrasive characteristic of fiberglass dulls cutting blades, and therefore, a cutting blade which has been used for cutting fiberglass cannot be used to cut polyester without sharpening or coating the blade. For this reason, fiberglass and polyester fiber cannot be fed together for cutting by the same cutting blades of cutter apparatus. It would be desirable to overcome this problem for purposes of obtaining a good mix of shorter lengths of the two.
A portable device adapted to break fibers into short lengths and to direct the same onto a surface being coated is disclosed in U.S. Pat. No. 3,011,257 to Bamberger, hereby incorporated by reference. Glass rovings are continuously drawn into the bite of oppositely turning rollers, one of which has circumferentially spaced chopping bars thereon which engage the other roller and break the fibers into short sections when passed therebetween.
Many other types of cutting devices and methods for dividing elongated material into shorter lengths are known. Specifically, reference should be had to U.S. Pat. Nos. 3,485,120 to Keith, 3,733,945 to Cook, 4,120,222 to Potter and 4,300,422 to Potter, all of which are hereby incorporated by reference. All of these cutters are broadly used for cutting tow of very high denier into staple length fibers. The cutter of the Keith patent includes a rotatable reel having outwardly facing cutting blades against which the tow is wound; a fixed pressure roller pressing upon the tow wound around the reel results in cutting of the innermost layers of tow by the cutting blade. As cutting progresses a wad of cut staple fibers is forced inwardly between adjacent pairs of blades. The other patents are directed to modifications of the Keith apparatus for removal of the cut fibers.